In this work we derive closed expressions for the head of frequency-dependent microscopic polarizability matrix in projector-augmented wave (PAW) methodology. Contrary to previous applications, longitudinal expression is utilized, resulting dielectric properties that are largely independent applied potentials. The improved accuracy present approach demonstrated by comparing and transversal a number cubic semiconductors one insulator, i.e., Si, SiC, AlP, GaAs, diamond (C), respectively....

Hybrid Fock exchange/density functional theory functionals have shown to be very successful in describing a wide range of molecular properties. For periodic systems, however, the long-range nature exchange interaction and resultant large computational requirements present major drawback. This is especially true for metallic which require dense Brillouin zone sampling. Recently, new hybrid [HSE03, J. Heyd, G. E. Scuseria, M. Ernzerhof, Chem. Phys. 118, 8207 (2003)] that addresses this problem...

Employing the random phase approximation we investigate binding energy and Van der Waals (vdW) interlayer spacing between two layers of bilayer transition metal dichalcogenides ${\mathrm{MoS}}_{2}$, ${\mathrm{MoSe}}_{2}$, ${\mathrm{WS}}_{2}$, ${\mathrm{WSe}}_{2}$ for five different stacking patterns, examine stacking-induced modifications on electronic optical/excitonic properties within GW with a priori inclusion spin-orbit coupling by solving two-particle Bethe-Salpeter equation. Our...

We present converged ab initio calculations of the optical absorption spectra single-layer, double-layer, and bulk MoS${}_{2}$. Both quasiparticle-energy (on level GW approximation ) calculation Bethe-Salpeter equation) explicitly include spin-orbit coupling, using full spinorial Kohn-Sham wave functions as input. Without excitonic effects, would have form a step function, corresponding to joint density states parabolic band dispersion in two dimensions. This profile is deformed by...

Abstract In magnetic fields up to 50 kOe and for photon energies greater than the band gaps light polarized with E ⊥ c ‖ oscillatory changes of reflectivity are observed on ZnO‐crystals at helium temperatures. The anisotropic reduced masses hole energy deduced from shift reflection maxima in dependence field ( H , ). influence Coulomb interaction holes electrons electron‐phonon Landau levels discussed. results compared valence structure wurtzite type crystals parameters ZnO previously reported.

We present an ab initio study of the lattice dynamics group-IV elemental semiconductors and insulators using a finite differences approach. The investigated solids include cubic diamond (C), silicon (Si), germanium (Ge), zero-gap semiconductor gray tin $(\ensuremath{\alpha}\text{-Sn})$. main objective this work is to examine performance screened hybrid functional (HSE) proposed by Heyd, Scuseria, Ernzerhof [J. Chem. Phys. 118, 8207 (2003); J. 124, 219906(E) (2006)] for calculating...

The band structures of $\text{In}\text{ }X$ ($X=\text{P}$, As, and Sb) are calculated using the hybrid HSE06 functional $GW$ with spin-orbit coupling effects included up to second order. Conventional local or semilocal density functionals predict an incorrect ordering for InAs InSb when is included. We show that inclusion one quarter exact exchange allows us very accurate gaps InP, InAs, InSb, i.e., 1.48, 0.42, 0.28 eV, respectively, in good agreement recent experiments. Furthermore,...

We present ab initio calculations on the structural and electronic properties of narrow-gap lead chalcogenides $\mathrm{Pb}X$ ($X=\mathrm{S}$, Se, Te). Particular emphasis is put correct description their exceptional compared to III-V II-VI semiconductors, such as very small magnitude band gap, unusual order gaps within series $[{E}_{g}(\mathrm{Pb}\mathrm{S})>{E}_{g}(\mathrm{Pb}\mathrm{Te})>{E}_{g}(\mathrm{Pb}\mathrm{Se})]$, high effective charge-carrier masses. Within standard...

We present the electronic band structures and dielectric tensors for a series of crystalline linear oligoacenes---i.e., naphthalene, anthracene, tetracene, pentacene---calculated within density functional framework. The dispersions, effective charge carrier masses, optical response are discussed as function oligomer length compared to previously reported calculations. total dispersions two topmost valence lowest conduction bands between 0.14 $0.52\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$,...

The transition from an indirect to a direct gap semiconductor in unstrained as well compressively and tensile strained ${\mathrm{Sn}}_{x}{\mathrm{Ge}}_{1\ensuremath{-}x}$ alloys is investigated function of the Sn content 0 \ensuremath{\le} $x$ 1 by means both very accurate supercell approach more approximate virtual crystal approximation (VCA). In local density we calculate bowing parameter lattice constant alloys. Provided that pseudopotentials suitable for VCA are used, random approaches...

Topological insulators are characterized by Dirac cone surface states with electron spins aligned in the plane and perpendicular to their momenta. Recent theoretical experimental work implied that this specific spin texture should enable control of photoelectron circularly polarized light. However, these reports questioned so far accepted interpretation spin-resolved spectroscopy. We solve puzzle show vacuum ultraviolet photons (50-70 eV) linear or circular polarization probe indeed initial...

We show how the optical absorption properties of organic molecular crystals based on finite units depend oligomer length. calculate dielectric tensor for first four linear oligoacenes by solving Bethe-Salpeter equation electron-hole Green's function. The exciton binding energy significantly decreases with size. While strongly bound excitons are present in naphthalene, carriers only weakly pentacene. This trend is understood terms increasing screening and spatial distribution wave

The Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional has been proven to yield lattice constants and energy gaps of semiconductors in better agreement with experiment than standard local semilocal exchange correlation functionals. latter underestimate the band many severely, i.e., case ZnO underestimation amounts 75% experimental value. In this work, we report on structure optimization study electronic gap wurtzite phase performed within density-functional theory using...

By solving the Bethe-Salpeter equation for electron-hole Green function crystalline anthracene we find lowest absorption peak generated by strongly bound excitons or a free pair, depending on polarization direction being parallel to short long molecular axis, respectively. Both excitations are shifted lower energies pressure. The physical difference of these is apparent from wave functions. Our findings major contribution solve long-standing puzzle about nature optical in organic materials.

Abstract The well‐known exciton reflectance spectra of ZnO at helium temperatures are changed drastically by surface layers. To explain the experimentally observed structure reflectivity a medium with harmonic oscillators (nonspatial dispersion) or spatial dispersion and an additional layer is calculated. either intrinsic exciton‐free impurity in which multiple reflections interference take place. From comparison experiment calculation following results obtained: firstly, free excitons has...

The pressure effect on the internal molecular orientation, electronic and optical properties of crystalline anthracene is calculated up to 10.2 GPa by performing density-functional calculations. As only input for our ab initio calculations we use lattice parameters experimentally determined x-ray powder diffraction under optimize geometry with respect three angles $\ensuremath{\theta},$ $\ensuremath{\chi},$ $\ensuremath{\delta},$ which define orientation molecules inside unit cell. For...

Abstract The reflection spectra of the ordinary and extraordinary polaritons near A 1 ‐, B ‐exciton resonances ZnO are presented for two geometries: normal planes inclined to c ‐axis at varying degrees, oblique as‐grown (10 I 10) faces. experimental theoretical compared. calculations based on a) dispersion relations derived from Fresnel's equation taking account spatial dispersion, b) Pekar additional boundary conditions combined with an exciton free surface layer. There indications...

The crystalline structure of anthracene (C14H10) under high pressure was studied performing angle dispersive x-ray diffraction experiments using synchrotron radiation in combination with Rietveld refinements and rigid body approximation. High hydrostatic applied up to 27.8 GPa a diamond anvil cell. Full structural information (molecular orientations lattice constants) is given 20.3 GPa. At the highest 22.7 unit cell volume decreased by 36.8%. Fourier transformation diffracted intensities...

The Cu-exchanged zeolite SSZ-13 is a highly active material in the selective catalytic reduction of nitrogen oxides and conversion methane to methanol. In this material, distribution sites present its characterization long standing challenge. contribution, we combine molecular dynamics simulations high-level first principles calculations obtain accurate phase diagrams, photoabsorption, photoluminescence spectra CuI compare them specifically designed experimental measurements. We start our...

We report on pressure-induced structural changes in crystalline oligo(para-phenylenes) containing two to six phenyl rings. The results are discussed with particular emphasis put the implications these intermolecular distances and molecular arrangement have important bulk properties of this class materials, such as optical response charge transport. performed energy dispersive x-ray diffraction a systematic study polycrystalline powders biphenyl, para-terphenyl, p-quaterphenyl,...

Abstract The magneto‐luminescence spectra of the fourfold n = 1 A‐exciton in ZnO up to H 5 T are reported. Zeeman splitting configuration ∥ c , k ⊥ c, E clearly demonstrates influence ‐linear energy terms allowed for ‐components perpendicular ‐axis 7 valence bands wurtzite structure. appropriate exciton coupling matrix is calculated. From comparison with experimental results A‐valence band slope C 2 × 10 −10 eV cm

The goal of this ab initio study is to investigate the role intermolecular interactions in molecular semiconductors. We discuss pressure-dependent electronic, optical, and structural properties biphenyl para-terphenyl crystals. These materials can be viewed as prototypes for conjugated optimize all internal parameters, including bond lengths orientation, a function pressure, where lattice parameters are taken from experiment. compare computed bulk modulus available experimental data....

In this work, the optical properties including excitonic effects of organic semiconductors investigated within an ab-initio framework are reviewed. particular, imaginary part frequency-dependent dielectric tensor has been calculated for several molecular crystals consisting short molecules and polymers, which comprise prime examples versatile class semiconductors. The electron-hole interaction included by solving Bethe–Salpeter equation two-particle Green's function. This approach allows...